1. Field of the Invention
The present invention concerns a method and an apparatus for controlling transmission ratio of a belt variator, in particular a belt variator in a transmission unit for a motor vehicle.
In particular, the invention concerns a method and an apparatus whereby the transmission ratio may be controlled according to two methods, namely a method whereby the transmission ratio is automatically altered as a function of different characteristics of speed and torque and such and a method whereby the transmission ratio is altered gradually as a result of signals given by the driver of the vehicle.
2. Description of the Related Art
With the second method, the transmission "shifts" in a manner similar to that of a conventional gearbox. It is desirable for certain applications that, instead of making use of the conventional automatic transmission, one may switch to the above-mentioned second method.
According to the second method, the signals for gearing up and gearing down, respectively, are given for example by briefly exerting a pressure on a gear lever in one direction to go into a higher gear and in the other direction to go into a lower gear.
Consequently, this method is sometimes called the "tip mode".
A known embodiment thereof is described in EP 0.697.548.